Control for two-temperature refrigerators



Oct. 25, 1938.

F A. HARSHBERGER CONTROL FOR TWO-TEMPERATURE REFRIGERATORS Filed Sept.29, 1955 WlTNE SE5:

Box I INVENTOR FRED H. HRRSHBERGER.

Patented Oct. 25, 1938 UNITED STATES CONTROL FOR TWO-TEMPERATURE RE-FBIGERATORS Fred A. Harshberger, Springfield, Masa, minor toWestinghouse Electric 3: Manufacturing Company, East Pittsburgh, Pa., acorporation of Pennsylvania Application September 29, 1936, Serial No.103,104

'iCiaims.

My invention relates to apparatus for controlling the operation of arefrigerating system having relatively high and low temperatureevaporators and it has for an object to provide improved apparatus ofthis character.

A further object of my invention is to normally effect refrigeration ofone of the evaporators of a multiple evaporator system, in preference tothe other evaporator, when both demand cooling, and to transferrefrigeration to said other evaporator when its temperature increases toan abnormally high value.

In practicing my invention, I provide relatively high and lowtemperature evaporators connected to a common condensing unit anddisposed for cooling the air in first and second zones of arefrigerator. Means is provided for effecting refrigeration of theevaporators, selectively, and temperature responsive elements associatedwith the respective zones of the refrigerator select the evaporator tobe operated.

During normal operation, the condensing unit is operated with the hightemperature evaporator in response to a demand for cooling from the hightemperature zone and, conversely, the lower temperature evaporator isoperated with the condensing unit in response to a demand for coolingfrom the low temperature zone. In the event of a demand for cooling fromboth of the refrigerated zones, one of the evaporators, such as, forexample, the low temperature evaporator is given preference. At suchtimes, the higher temperature zone is not being refrigerated and mayrise in temperature to an abnormally high and undesirable value. Meansis provided for transferring refrigeration to the higher temperatureelement when the temperature of the higher temperature zone rises to apredetermined abnornal value. When said abnormal temperature has beendepressed to a predetermined value, normal control over the evaporatorsis re-established with the lower temperature zone having preference overthe higher temperature zone.

The foregoing andother objects are effected by my invention as will beapparent from the following description and claims taken in connectionwith the accompanying drawing forming a part of this application, inwhich:

The single figure of the drawing shows diagrammatically atwo-temperature refrigerator having my improved control apparatusapplied thereto.

Referring to the drawing, I show a two-temperature refrigeratorgenerally indicated at It, and including relatively high and lowtemperature chambers II and i2, respectively. Evaporators I3 and I4 aredisposed within the chambers II and I2, respectively, for abstractingheat therefrom. The high'temperature evaporator i3 operates, primarily,to 0001 articles of food stored in the chamber ii and the lowtemperature evaporator I4 operates to congeal fluid within containersshown at Ma and to maintain the temperature of the air in the chamber l2at a relatively low value. Articles to be maintained in a frozencondition or at a low temperature are stored in chamber l2 as is wellunderstood.

The evaporators l3 and i4 define elements of a refrigerating systemhaving a common condensing unit I5, preferably of the compression type.The latter may include a hermetically sealed compressor (not shown)disposed within a hermetic casing it and driven by a motor, a winding ofwhich is shown at 20, and disposed within the casing it. As ahermetically sealed motor driven compressor of the type shown is wellknown in the art, no further description of it is deemed necessary. Theterminals of the motor are shown at IT and Ho. The condensing unit l5includes a condenser i3 cooled in any suitable manner as, by a fan l3,and receiving compressed refrigerant gas from the compressor through aconduit 2!. I

Liquid refrigerant is conveyed to the evaporators l3 and I4 through abranched conduit 22 and vaporized refrigerant is withdrawn from theevaporators l3 and i4 through conduits 23 and 24, respectively. Therefrigerating system which I have shown is of the well known floodedevaporator type having low side floats shown at 25 and 28 forcontrolling the admission of condensed refrigerant to the evaporators l3and i4, in accordance with the levels of the liquid therein. A valvestructure generally shown at 21 communicates with the suction conduits23 and 24. and with the suction side of the compressor by means of aconduit 23. The valve structure 21 is selectively operated to effectcommunication between the conduit 23 and either conduit 23 and 24depending upon which evaporator is being refrigerated.

As shown, the valve structure 21 includes inlet chambers 3| and 32 towhich the suction conduits 23 and 24 are connected, and an outletchamber 33 communicating with the suction conduit 28 of the compressor.Valve members 34 and 33 control communication between the chamber 31 or32 and the outlet chamber 33. A solenoid 36 actuates the valve members34 and 35 and, when energized, eil'ects communication between theconduits 23 and 28 whereby the evaporator I3 isrendered active. Whendeenergized, the solenoid 36 connects the conduits 24 and 28 so that theevaporator I4 is active.

During operation of the condensing unit |5, vaporized refrigerant iswithdrawn by thecompressor'from either evaporator l3 or l4 throughconduit 28 depending upon whether the solenoid 36 is energized ordeenergized. The withdrawn gas is compressed to a relatively highpressure in the condenser l8 and is cooled and condensed. Liquidrefrigerant is admitted to the evaporators l3 and I4 through theirassociated float valves 25 and 26 and is maintained at a substantiallyconstant level in the evaporators. The compressor maintains the pressureof the refrigerant in the evaporator at a relatively low value so thatthe refrigerant vaporizes at low temperature and abstracts heat from theevaporators in a well known mannert,

The foregoing defines a conventional refrigerating system having a pairof flooded evaporators operating at different temperatures and connectedto a common condensing unit in such manner that they are selectivelyoperated. My improved control apparatus will now be applied to thissystem. .It is to be understood that the system disclosed is shown byway of example and that my improved control apparatus may be applied toother two-temperature systems having either flooded or so-called drytype evaporators with means for efiecting vaporization in theevaporators, selectively.

The chamber cooled by the high temperature evaporator 3, is maintainedbetween predetermined temperature limits preferably by means of agas-type thermostat, generally indicated at 38. The thermostat 38includes an expansible bellows 39 connected to a bulb 4| by means of atube 42. As is well understood, thermostats of this type have a volatilefluid contained in the bulb 4|, the pressure of which is a function .ofthe temperature of the bulb. Accordingly, the bellows 39 expands andcontracts as the evaporator l3 and bulb 4| increase and decrease intemperature, respectively. In this connection, it will be understoodthat the thermostat 38 may be made responsive to the temperature of theair in the chamber instead of the temperature of the evaporator 3 bydisposing the bulb 4| in the air within the chamber Expansion of thebellows 39 is opposed by a spring 43 which may be adjustable for varyingthe temperature at which the thermostat operates. A lever 44 pivoted at45 is actuated by the bellows and carries movable contact members 46 and41 forming parts of switch structures 48 and 49 respectively. Theswitches 48 and 49 include stationary contacts 5| and 52, respectively.

The operation of the switch 48 is such that the contacts 46 and 5| closeand open to initiate and terminate operation of the condensing unit |5in response to predetermined high and low temperatures of the evaporatorl3, respectively. The periods of operation when the temperature of theevaporator I3 is between these limits may be callednormal operatingperiods, during which the movable and stationary contacts 41 and52 ofswitch 49 remain in engagement. As shown, this is accomplished by makingthe movablecontact 4! of such length that it continuously engages thestationary contact 52 regardless of normal amplitudes of the bellows.However, during an abnormal operation, or when the temperature of theevaporator l3 increases to an abnormally high value, the movable contact4'! is disengaged from the stationary contact 52 due to the increasedamplitude of the bellows 39. The purpose of this operation of the switch49 will be made apparent hereinafter.

The temperature of the evaporator I4 and chamber 2 is controlled. byajthermostat 53, preferably of the gas type. The thermostat 53 includesa bulb 54 which may be secured to the evaporator M and connected to abellows 55 by a tube 56. A lever 51, pivoted at 58, is actuated by thebellows 55 and carries a bridging contact 59 forming the movable memberof a switch 6|. The latter includes stationary contacts 62 which arebridged by the member 59 as the temperature of the evaporator l4increases to a. predetermined value. The contacts 59 and 62 aredisengaged as the temperature of the evaporator is depressed to thedesired value. The thermostat 53 may include an adjustable spring inopposition to the bellows, whereby the temperatures at which the switchoperates maybe varied. The switch 6| controls operation of thecondensing unit I 5 and, therefore, refrigeration of the evaporator l4.

Electrical energy for the motor of the condensing unit I5 is obtainedfrom line conductors L1L2 under control of the switches 48, 49, and 6|.As shown, the switches 49 and 6| are connected in series in a conductor65 extending from the line conductor L1 to the terminal I! of the motor.The opposite terminal |'|a of the motor is connected to the lineconductor L2. A conductor 66 controlled by the switch 48 extends fromthe line conductor L1 to the motor terminal I! and includes the solenoid36.

It will be apparent from the foregoing that the motor of the condensingunit may be energized by two circuits, one of which includes theconductor 65 and the switches 49 and 6| and the other of which includesthe conductor 66, the switch 48 and the solenoid 36.

Operation In the position of the apparatus shown in the drawing,the'condensing unit I 5 is inactive as the temperature of theevaporators I3 and H are below the values at which the thermostats 38and 53 operate to energize the motor winding 29. Assume that thetemperature of the evaporator |4 rises sufliciently to close the switch6| of the thermostat 53. The winding 29 of the motor is energizedthrough a circuit including line conductor L1, conductor 65, closedswitches 6| and 49, winding 29, and line conductor L2. The solenoid 36is deenergized so that the evaporator suction conduit 24 communicateswith the suction conduit 28 of the condensing unit l5 and, therefore,the evaporator I4 is refrigerated. The thermostat 53 opens the switch 6|in response to a predetermined low temperature of the evaporator l4whereby the motor winding 29 is deenergized and refrigeration of theevaporator 4 is terminated.

In responseto a predetermined high temperature of the evaporator I3, thethermostat 38 operatesto close the switch 48 and, therefore, effectenergization of the solenoid 36 and motor winding 29 through a circuitincluding line conand 28 are communicating. Operation of the condensingunit isinitiated and refrigeration of the high temperature evaporator II is effected. The condensing unit operates until the temperature of theevaporator I3 is depressed to a predetermined minimum value at which thethermostat 38 opens the switch 48 and effects deenergization of themotor winding 20 and the solenoid l6. Circulation of refrigerant ceasesand the valve structure 21 is returned to the position shown in thedrawing.

In accordance with my invention, one of the evaporators is givenpreference over the other when both demand cooling. I have disclosed acontrolin which the colder evaporator I4 is the preferential evaporator.In the event that both thermostats B8 and 53 close their respectiveswitches 48 and SI in response'to demands for cooling from bothevaporato'rs I3 and I, the motor winding 20 is energized through theaforementioned circuit including the conductor 65, and the solenoid 38is deenergized due to the shunt formed thereacross by the conductor 65and closed switches 6| and 48. Refrigeration of the colder evaporator I4is therefore effected in preference to the warmer evaporator II. Whenthe temperature of the evaporator I l is depressed to the desired value,the thermostat 53 opens its switch Iii so that the shunt circuit acrossthe solenoid is opened. The condensing unit I! continues to operate asthe motor winding 20 is energized by the afore-mentioned circuitincluding-the conductor 66 and solenoid It. Refrigeration of theevaporator I3 is effected as the solenoid '36 actuates the valve 21 tothe position wherein suction conduits-23 and 28 are communicating.

There may be times when the colder evaporator I4 is being refrigeratedfor a relatively long period of time during which the warmer evaporatorI3 is inactive. Accordingly, the temperature of the evaporator I3 andof, the articles of food stored in the chamber II may rise to anabnormal and undesirable high temperature and food spoilage may occur.In accordance with my invention, I preclude the possibility of foodspoilage by transferring refrigeration to the evaporator I3 incidentalto a rise in its temperature to a predetermined value, higher than thenormal value at which the switch 48 is closed.

Assume both evaporators I3 and I4 are calling for cooling. Thecondensing unit I! operates to refrigerate the evaporator I! in themanner described, heretofore. and the evaporator I3 is inactive. Thetemperature of the evaporator I3 and the contents of the chamber IIcontinue to rise and expansion of the bellows continues. When thetemperature attains a predetermined value, the bellows 39 opens thecontacts 1 and I! of switch while the switch It remains closed.Accordingly. the shunt circuit including the switches 40 and II andconductor S! is opened and energization of the solenoid is efhaveprovided an improved control for a mul- "tiple evaporator refrigeratingsystem wherein refrigeration of one evaporator is given preference overanother when both call for refrigeration with provisions for givingpreference to saidother evaporator incidental to an abnormal rise in itstemperature. I have disclosed a system wherein the colder evaporatornormally has preference but it will be understood that preference maynormally be given to the higher temperature evaporator.

The various control instrumentalities are shown in their simplest formfor the sake of cleamess and it is to be understood that various otherforms of instruments per se, which preferably include quick operatingswitch members, may be employed in my improved system.

I have disclosed a refrigerator having two separate compartments cooledby respective evaporators, but it will be understood that arefrigerator, having different zones of a single compartment cooled byseparate evaporators, may be satisfactorily controlled by my improvedcontrol.

While I have shown my invention in but one form, it will be obvious tothose skilled in the art that it is not so limited, but is susceptibleof various changes and modifications without departing from the spiritthereof, and I desire, therefore, that only such limitations shall beplaced thereupon as are imposed by the prior art or as are specificallyset forth in the appended claims.

Wliat I claim is:

1. In refrigerating apparatus, the combination of a refrigerator cabinetembodying different zones to be refrigerated, means for obtainingdifl'erent refrigerating temperatures in said different zones of therefrigerator cabinet, means for efiecting refrigeration of one of saidzones in preference to another of said zones during normal temperaturevariations in said respective zones, and means for effectingrefrigeration of said other zone in preference to said one zone when thetemperature in said other zone rises abnormally.

2. In a control system for a refrigerator having relatively high and lowtemperature cooling compartments, the combination of means forselectively efiecting refrigeration of the high and low temperaturecooling compartments, and temperature responsive means associated withsaid compartments for controlling the operation of the refrigeratingmeans and normally active to effect refrigerationof one of saidcompartments in preference to the other when both require cooling, saidtemperature responsive means including means for effecting refrigerationof said other compartment in preference to said one compartment when thetemperature of the other compartment rises to an abnormally high value.

3. In a control system for refrigerating apparatus, the combination ofastructure defining first and second cooling chambers, first and secondcooling elements disposed for cooling the chambers, respectively, meansresponsive to a predetermined high temperature prevailing within thefirst compartment for effecting circulation of refrigerant through itsrespective element, means responsive to a predetermined high temperatureobtaining within the second compartment for effecting circulation ofrefrigerant through its respective element, said temperature responsivemeans being so arranged that circulation of refrigerant is effected inthe second element in preference to the first when the temperaturesprevailing in both compartments are above said predetermined values,said temperature responsive means associated with the first compartmentincluding means actuated in response to an abnormally high temperatureprevailing within the first compartment for effecting circulation ofrefrigerant through its associated element and for terminatingcirculation of refrigerant through the element of the secondcompartment.

4. In a control system for refrigerating apparatus having first andsecond cooling chambers, first and second evaporators disposed,respectively, in the chambers for cooling the same, means for condensingrefrigerant for vaporization in the evaporators, means responsive to apredetermined temperature prevailing in the first chamher for effectingvaporization of refrigerant in its respective evaporator, meansresponsive to a second predetermined temperature prevailing in thesecond chamber for efiecting vaporization of refrigerant in itsrespective evaporator, said temperature responsive means being soarranged that vaporization of refrigerant is efiected in the secondevaporator in preference to the first when the temperatures prevailingin both chambers are above said predetermined values, and a deviceactuated by said first temperature responsive means in response to anabnormal temperature, higher in value than said first predeter-- minedtemperature, for rendering the second temperature responsive meansinactive, whereby vaporization of refrigerant is initiated in the firstevaporator and terminated in the second, said device rendering thesecond temperature responsive means active when said abnormaltemperature has been depressed to a normal value.

5. In a, control system for a refrigerator having relatively high andlow temperature cooling chambers formed therein, the combination offirst and second evaporators for cooling the air in said chambers,respectively, means for translating refrigerant to the evaporators andselectively efiecting vaporization therein, means responsive totemperatures prevailing within the respective chambers for controllingsaid refrigerant translating means, said temperature responsive meansbeing so arranged that refrigerant is translated for vaporization in oneof the evaporators in preference to the other when the temperaturesobtaining within both chambers are above values which call for coolingthereof, and means associated with the temperature responsive means foreffecting translation of refrigerant to said other evaporatorior vaporization therein and for terminating vaporization of refrigerant in saidone evaporator when the temperature obtaining in the chamber cooled bysaid other evaporator increases to a predetermined value.

6. In a control system for refrigerating apparatus having first andsecond cooling chambers, first and second evaporators disposed,respectively, in the chambers for cooling the same, means for condensingrefrigerant for vaporization in the evaporators, a mechanism movable tofirst and second positions wherein refrigerant is delivered forvaporization in the first and second evaporators, respectively, meansresponsive to, a predetermined temperature within the first compartmentfor actuating said mechanism to the first position, means responsive toa predetermined temperature within the second compartment forpositioning the mechanism in its second position independently of thefirst temperature responsive means, and means responsive to an abnormaltemperature within said first compartment higher than said firstmentioned predetermined temperature, for rendering said secondtemperature responsive means inactive to control said mechanism, wherebyrefrigerant is delivered for vaporization in the first evaporator duringperiods when the abnormal temperature prevails-and independently of thesecond temperature responsive means. I

7. The combination of a cabinet structure having first and secondchambers formed therein, first and second evaporators for cooling thechambers, respectively, means for condensing refrigerant forthe'evaporators, a device movable to first and second positions forefiecting vaporization of refrigerant in the first and secondevaporators, respectively, said device being biased to its secondposition and having a solenoid for actuating it to its first positionwhen energized, means responsive to a predetermined temperature withinthe first chamber for energizing said solenoid and for effectingoperation of therefrigerant condensing means, means responsive to apredetermined temperature within the second chamber for eifectingoperation of said refrigerant condensing means and for rendering saidsolenoid incapable of energization and means responsive to an abnormaltemperature obtaining within the first compartment, which temperature ishigher than said first predetermined temperature, for effectingoperation of the refriger- FRED A. HARSHBERGER.

